"Blanc-Oh!", my distraction

[ntsqd]

I had looked and felt the area around the rear system RPV every time I had cause to look at all. Since I had opened up the RPV to defeat it's function it was suspect until proven not to be. Until this morning, no observed wetness of any kind.

There were several of the -3AN fittings that went another ~1/16th turn tighter. No sign of fluid at any of them except for maybe one of them. That is one that I may try the Scott towel trick on, just to be sure that it isn't leaking. There's an odd stain on the POR-15 near it that only makes sense if it were leaking badly and under a fair amount of pressure, but I've never seen it wet either.

Bled the brakes, again!, and took it on a ~200 mile drive over a mountain pass and back. Brakes feel as good as right after bleeding them. Will be driving it in next week's commute to see if this lasts.

[ntsqd]

Brake pedal travel has increased enough that it's clear that it now has air in it again.


I found the Ford p/n for the OEM RPV and found a vendor supposedly with inventory. These do not come with a new or rebuilt master cyl. They screw into the side of the m/c with an o-ring seal. New m/c's supply a new o-ring only. Once the replacement RPV assembly is here I will be taking the the existing one back apart and looking into how it can be made to be one piece (they are a body, a cap, and some pieces inside). This will likely either involve silver-solder or silicon-bronze filler rod.

An aspect of the RPV body is that it has some considerable interior volume. Ever since gutting it I've wondered if it could be trapping air as bleeding the rear system isn't fast or easy. (I'm 1/2way thru the third quart of brake fluid in dealing with this!) The next iteration of that part will be a good bit smaller and not have that volume.

[ntsqd]

I dug into the mildly weeping RPV and made SW models of the RPV body and cap to get a better idea of what it looked like inside when assembled.

First thing that I noticed during the disassembly is that the seal between the cap and the body of the RPV housing is a cup type seal rather than a square, round, or other type of o-ring, AND that it was installed what I think would be backwards. The cup was facing away from the pressure, not towards it as it would need to be for the pressure to force the seal against the sealing surfaces. I have no memory of disturbing this seal the first time that I pulled this thing apart, but that doesn't mean that I didn't. So I could have put it on backwards w/o realizing it or could have been backwards from the start. Can not use it again as it did not survive being removed from the cap. Shown below only for reference.



The gray part is made from 6061 T6 that I then annealed dead soft so that it will act like a crush washer when the cap is tightened. That's the plan anyway, and it appears to have worked. I set the crush column's length to have a .05" gap where the cap's step meets the end of the body when tightened by fingers only. After tightening it with a wrench as much as I though that I could get away with that gap is about .01" by eyeball. It's back in the m/c and everything is connected. Plan is to bleed it tonight and test drive it.

[ntsqd]

I'm about 225 miles in on testing this latest fix for the problem and it appears to be working. The plan is to gravity bleed the rear brakes at 300 miles. If no air bubbles then I'll do it again at 500 miles. If no air bubbles then I'm going to call this fixed!
FWIW a gravity bleed was not something that it would do in the past. That alone is a big improvement.

[ntsqd]

Got the gravity bleed done at ~335 miles. No bubbles for a count of 40. Pedal is still firm and high. I'm going to gravity bleed it again at ~500 miles, but I'm thinking that this has finally been put to bed.

Need to build the mount for the OBA/OX locking rear diff compressor next.

[SteveG]

That's great! I've gravity bled A LOT of things... I think it's an under-rated method!

[ntsqd]

It is slow, I think most discount it because of that. The thing is, that for a simple maint. bleed it's not that slow. Everyone should build a peanut butter bleeder. Then you can crack open a new system with it connected and let it go for a while without making a mess.

Prior to making the insert the system would not gravity bleed. Fluid flow was solid, but by the pedal feel there was obviously still air in it.

I should be at 500 miles sometime on Tuesday. I'll do one more gravity bleed then. Here's hoping.....

In the mean time I've got the mount for the OBA compressor fairly roughed out. After a little detailing it will be ready for paint. Then one piece of plumbing and a little wiring and it will be done.

Next will be to fix the rear window wiring. That'll be fun. My hands don't fit down in there.

[ntsqd]

Oh yeah, the peanut butter bleeder pic:

[ESHALLBETTER]

Can you explain the insert and it allowing it to bleed? I've done brakes with the handheld vacuum, and I've seen gravity bleeding one with a single hose into a bottle of fluid, but I can't quite wrap my head around your system.

[ntsqd]

The insert (gray part) goes inside the body of the OEM Residual Pressure Valve after it's guts have been removed and eliminates some of the captured volume in there. The angle in the drawing above is the installed angle. Can see where there are high spots inside it that would capture air. The bigger issue was that the seal between the purple and the green part wasn't working perfectly. It allowed enough air to enter the system over ~250 miles that the rear brakes didn't work at all. I annealed the insert to be dead soft. When everything was just hand tight that outer gap between the green and purple parts measured .05" By the time I had tightened the green part into the purple part as tight as I thought I should that gap measured .01" The insert is effectively a crush washer sealing the two parts so that fluid can't get out and air can't get in while at the same time eliminating spots where air would get caught and not want to bleed out.

The peanut butter bleeder is just a bigger jar to bleed into. Can use it as just a container to keep the mess to a minimum; or can connect the short tube to a vacuum source to vacuum bleed the system. A pump if you must, I prefer to connect it to the intake manifold. Not seen in the pic is the long hose that allows that to happen.

[ntsqd]

~640 miles, pedal is still as when it was first bled. I won't be able to do a gravity bleed check until the weekend, but I think this one is solved!

[ESHALLBETTER]

Thanks for the extra detail. Good to hear that you seem to have it worked out!

[Becks_Bronco]

any more details on this OBA system?

[ntsqd]

Ask and ye shall....

Puma 12VDC compressor, Viair 2.5 receiver tank, gigavac compressor power contactor controlled by an adjustable Automation Direct pressure switch, ARB locker solenoid re-purposed to be an unloader. Wiring default is on with the key, switchable off should the need arise. Compressor power is from the 'house' battery.
Plumbing is all 3/8" truck air brake system urethane tubing and DOT "Push to Connect" fittings. QD's at the rear bumper, under the hood (on the controls/distribution manifold) and on each side under the doors.

The side QD's are behind little rock & mud deflectors like the one seen here:


House Battery:


Controls/Distribution manifold, the pinched-off & heat-sealed green tube has been replaced - it was just to keep grit out, the plug has been replaced with the regulator for the OX Locker system.


The manifold little further along:


Air tank location, compressor will live above it:

[ntsqd]

Oh yeah, stumbled onto these fittings: https://www.amazon.com/gp/product/B09B45W496/ and plumbed one to the receiver tank from inside the fuel filler area. It is the only leg in the system lacking the DOT fittings and tubing. It allows me to fill the system with shop air before a trip. From previous testing the system will hold above 100 psi for about a week from a ~130 psi charging. Neither of my previous OBA systems will do that. The only real difference is the tubing and the fittings.

[Becks_Bronco]

nice!

My '22 Ram 2500 has the factory rear air suspension, and I honestly couldn't tell you when the compressor runs. There is a small tank under the passenger floor and it must be incredibly well isolated. Been thinking of grabbing one of the setups and installing it somewhere on the bronco for OBA.

[Becks_Bronco]

Oh yeah, stumbled onto these fittings: https://www.amazon.com/gp/product/B09B45W496/ and plumbed one to the receiver tank from inside the fuel filler area. It is the only leg in the system lacking the DOT fittings and tubing. It allows me to fill the system with shop air before a trip. From previous testing the system will hold above 100 psi for about a week from a ~130 psi charging. Neither of my previous OBA systems will do that. The only real difference is the tubing and the fittings.

Thats pretty cool. I have access to DOT fittings and tube, I may have to look into using that.

[ntsqd]

Not sure that an air ride compressor is going to be very happy about refilling aired-down tires. Decades ago Cadillac's came with an easy to get air ride compressor and a lot of the guys on a Toyota 4x4 list were using them for a tire compressor. They didn't live very long doing that.
Flip side is that my neighbors know when the Puma in my 4rnnr starts up. It is not a quiet compressor.

I still have the almost peanut sized receiver tank that the compressor came bolted onto. I've debated what to do with it. Currently the OX Locker air system has no stored air volume, it draws directly from the 2.5 gal tank. I'd like to have some volume in it between the regulator (system is ~130 psi, OX wants ~90 as I recall) and the pneumatic switch. The Puma tank is just too big for that.

[ntsqd]

Minor updates:

The brakes continue to perform beyond my hopes. The only problem is that all of those miles with front brakes only have used up the cheap front pads. In spite of my trying to use the trans for compression braking as much as possible, they got pretty warm coming down out of Cerro Gordo last Feb. I've got the squealers doing their thing. Got a set of pads from Napa that appear to be made by Performance Friction. I hope their low temperature performance is good or I'll be putting them on the '73 SBSS Chevy.

The OBA for the OX locker and the air horn is three wires away from being operational. Puma compressor is mounted and plumbed. It's connected to ground and the contactor. I just need power from the nearby 80A breaker, ground for the contactor, and pressure switched power from the engine bay to make it work.

Some odd shift points happened and it tripped a code. TPS is going out, again. This is the second one in a bit more than a year. No idea where I got this one, am trying NAPAonline to see if I can get better parts and service than Rock Auto.

[Becks_Bronco]

Minor updates:

The brakes continue to perform beyond my hopes. The only problem is that all of those miles with front brakes only have used up the cheap front pads. In spite of my trying to use the trans for compression braking as much as possible, they got pretty warm coming down out of Cerro Gordo last Feb. I've got the squealers doing their thing. Got a set of pads from Napa that appear to be made by Performance Friction. I hope their low temperature performance is good or I'll be putting them on the '73 SBSS Chevy.

The OBA for the OX locker and the air horn is three wires away from being operational. Puma compressor is mounted and plumbed. It's connected to ground and the contactor. I just need power from the nearby 80A breaker, ground for the contactor, and pressure switched power from the engine bay to make it work.

Some odd shift points happened and it tripped a code. TPS is going out, again. This is the second one in a bit more than a year. No idea where I got this one, am trying NAPAonline to see if I can get better parts and service than Rock Auto.

Is the TPS available in a motocraft part?